A so-called hybrid vehicle that is driven by an internal combustion engine and an electric motor has been focused. In the hybrid vehicle, the electric motor functions as a generator to regenerate electric power (hereinafter merely referred to as regenerate power), and store the electric power during deceleration. The stored electric power is utilized to generate driving force for accelerating the vehicle or driving the vehicle.
Some hybrid vehicles have an automatic transmission. The automatic transmission is also referred to as a transmission below.
In this case, a clutch that transmits power or cuts the transmission of power can be provided between the internal combustion engine and the electric motor.
When a driver drives a vehicle on a long downgrade, the driver disengages the clutch to execute regeneration, and brake is applied by torque (hereinafter referred to as regeneration torque) generated by the regeneration of the electric motor.
When an accelerator pedal is slightly operated during the regeneration with the clutch being disengaged in the hybrid vehicle, the clutch is engaged for acceleration. During the engagement of the clutch, the rotational speed of the engine slightly increases from the speed in the idling state, and with this state, the clutch is engaged, in order not to apply shock to the vehicle.
There has conventionally been proposed a parallel hybrid vehicle including a battery temperature sensor that detects a state of a battery, an HVECU, a vehicle speed sensor that detects a state of the vehicle, an engine rotational speed sensor, an accelerator pedal opening degree sensor, and an FI/AT/MGECU that changes required values of an engine and a motor based on the accelerator pedal opening degree, and that determines whether a fuel supply to the engine is stopped based on the condition of the vehicle, wherein a fuel-cut state is kept when the vehicle is reducing speed, and the accelerator pedal opening degree is equal to or smaller than a predetermined opening degree, and until the accelerator pedal reaches the predetermined opening degree, a target torque obtained based on the accelerator pedal opening degree is controlled by the MOTECU (see, for example, patent literature PTL1).